Improvement in machines for the manufacture of screws



3Sheets-Sheer. 1.

Patented March 27,1877.

T. RICKETT. mcnmns FOR. THE MANUFACTURE OF SCREWS. No.18 8,9 49.

3 Sheets-Sheet Z.

T. RICKE'IT.

MACHINES FOR THE MANUFACTURE OF SCREWS.

Patented March 27,1877.

3 Sheets-Sheet 3.

T. RICKETT.

MACHINES FOR THE MANUFACTURE OF ScEEWS. No. 188,949. Patented March27,1877.

FIG-J1]:

N- PETE-R9, PHOTO-LITHOGRAPNER, W'ASHINBTDN. I v C.

UNITED. STATES PATENT THOMAS RIOKETT, or NoRTHFiELD, NEAR BIRMINGHAM,ENeLANn.

IMPROVEMENT IN MACHINES FOR THE MANUFACTURE OF SCREWS.

Specification forming part of Letters Patent No. 188,949. dated March27, 1877; application filed February 27, 1877.

. accompanying drawings.

My invention consists of the new or improved machinery hereinafterdescribed for the manufacture of screws, by the action of which saidmachinery on the rod or bolt to be made into a screw a screw-thread isimpressed upon the said rod or bolt without the cutting away of anyportion of the metal of the said rod or bolt.

The said machinery consists, essentially, of rolls having screw-threadscut uponthem, by and between which rolls the rod or bolt to be made intoa screw is operated upon. Pressure being applied to therolls,their'rotatory motion is communicated to the rod or bolt situatedbetween them, with its axis parallel to their axes, and thescrew-threads on the 'rolls are impressed on the rod or bolt, which isthus converted into a screw.

I use three rolls, with their axes parallel to each other. Two of therolls are placed as close together as posible in the same plane,

with the third roll above and midway between them. The rod or bolt to bescrewedis placed between the three rolls, and the said rolls are made torotate in the same direction. The upper roll is caused to approach thetwo lower rolls by mechanism, which preserves the par allelism of thethree rolls. By the action of the parallel rolls the sharp edge of thethreads of the said rolls are forced into the bolt, forming groovestherein, and raising the metal between the grooves until the threads ofthe rolls are exactly reproduced in the bolt. The

roll-threads groove the bolt to about half their depth, and theremainder of the thread is raised or forced up by the metal displaced inthe embedding of the roll-threads. By this method bolts of any lengthless. than that of the rolls can be made by a few rotations of therolls.

The bolts may be operated upon either hot or cold; but I prefer tooperate on the bolt tion of the machine.

while cold, the density and strength of the metal being greatlyincreased by the rolling action when the metal is operated upon in thecold state.

I make the rolls of steel, hardened and tempered, the threads being outupon them to the depth required on the screws to be made. When the rollshave the same diameter as the screws to be made, only one continuousscrewthread is made on each roll; but when the rolls are of largerdiameter than the screw to be made, more than one thread is made on eachroll, the number of threads on the rolls increasing as their diametersincrease. Thus, if the rolls have double the diameter of the screws,they have two continuous screwthreads each-that is, the threads formedare those of a double-threaded screw. Ifoftreble the diameter, they havethree screw-threads, and so on. When rolls of small diameter areemployed, I support or back them up by larger rolls.

Screws of steel, iron, brass, copper, or other metals and alloys can bereadily made by the use of the said machinery.

I will now proceed to describe, with reference to the accompanyingdrawings, the manner in which my invention may be carried into elfect.

Figural represents, in front elevation, and Fig. 2 in side elevation,machinery constructed according to my invention for the manufacture ofscrews by impressing a screwthread upon a plain rod or screw or boltblank.

The said machinery consists essentially of three rolls, a b 0, havingscrew threads out upon their peripheries, the axes or shafts 0!, b c ofthe said rolls being parallel to each other, and working in bearings inthe uprights d d. The peripheries of the said rolls a b c are concentricto their axes or shafts, and the construction of the said rolls ishereinafter particularly described.

The axes or shafts a b of the lower rolls a b are situated in the samehorizontal plane, and the third roll a is situated above and midwaybetween the said rolls a b. (See Fig. l.) The upper screwed roll 0 hasan automatic rising and falling motion given to it, so that it is madegradually to approach to and recede from the lower rolls a b during theac- The lower rolls a I) are adjustable by the set-screws a. b. The axis0 of the rising and falling roll a is carried in the bearings 0 c",which are capable of slidlng upon the uprights d d of the machine. Abovethe shaft 0 of the top roll a is a. parallel shaft, q, formed with aneccentric, q, between the bearings of the shaft. Working on theeccentric g is a metal strap, 1*, the joint ends or pivots g g of whichengage in the sliding bearings 13 0 in which the shaft 0 of the upperroll 0 works so that by the rotation of the said shaft q, and the actionof the eccentric q and strap 1', the upper roll 0 is made gradually toapproach to and recede from the lower rolls a b. The bearings of theshaft q are adjusted by the screws and screw-nuts s. The shaft q makesone revolution only while the rolls a b c are making severalrevolutions. The rolls a b c and the eccentric shaft q are driven by thefollowing arrangement of gearing: On the end of the shaft 0 of the upperroll 0 is a large toothed wheel, 0 receiving motion from any primemover. Or the said shaft 0 may be driven by a pulley and band. On thesaid shaft 0 is a toothed wheel, 0 which gives motion through thetoothed wheels 0 c, and pinions c and c to the bottom rolls a b.

In Fig. 2 the toothed wheel 0 is omitted. The shaftq is driven from theshaft of the toothed wheel 0 by the toothed gearing, partly indicated indotted lines in Fig. 1-that is to say, on the shaft of the wheel 0" is apinion, 0 which gears with the toothed wheel o On the shaft of the wheel0 is a pinion, o which gears with the toothed wheel 0 on the shaft q.The rising and falling of the upper roll a is thus automatic, and may bevaried by the use of the differential gear to suit different pitches ofscrews.

The action of the machine is as follows: The top screwed roll 0 being atits highest point, the plain rod or screw blank to be screwed isintroduced between the rolls a, b c. As the top roll 0 descends the rodor blank is seized between it and the bottom rolls a b. A rotatorymotion is thereby communicated to the rod or blank by the rotation ofthe said rolls, and screw-threads are impressed upon it, and when thetop roll has reached its lowest point a perfect screw thread will havebeen impressed upon the rod or blank by the said roll cin conjunctionwith the bottom rolls a b. A bolt marked, t, is represented in the actof being screwed by the operation of the rolls a b c. On the rising ofthe roll 0 the screwed bolt is released, and may be removed from themachine, and another plain rod or blank introduced between the rolls,and screwed in the manner described.

The feeding of the blanks to the rolls may either be efl'ectedautomatically or by hand.

I do not limit myself to any particular ratio between the diameter ofthe rolls, by which the screw is formed, and the diameter of the bolt tobe operated upon; nor do I limit myself to any particular rate-ofdescent of the upper roll 0 relative to the velocity of rotation of therolls; but I have found the proportions represented in the drawingsbetween the rolls and the bolt to be screwed to answer well inpractice-that is to say, the rolls a b 0 have a diameter three times asgreat as that of the bolt t to be operated upon. I have also found therate ofdescent of the upper roll 0 compared with the velocity of therolls a, b c, which rate is produced by the atl rangement of gearin grepresented in the drawing, to answer well in practice-that is, the rolla descends from its highest to its lowest position during the timeoccupied by the rolls a b 0 in making three rotations.

In forming the screw-threads on the rolls a b c I give to the saidthreads on the rolls a pitch, which is to the pitch of the thread to beproduced on the bolt as the diameter of the rolls is to the diameter ofthe bolt to be screwed. Thus, the rolls represented in the drawing havea diameter three times as great as that of the bolt to be screwed, andthe rise of the threads on the rolls is three times as great as thepitch of thread to be produced on the bolt. By the pitch of the thread Imean the distance between the summit or crest of one thread and thesummit or crest of the next thread, and by the rise I mean the distancetraversed along the roll by one convolution, the distance referred tobeing measured in a line parallel with the axis of the roll.

From this method of construction it follows that there will be severalscrew-threads on the roll, the number of the said screw-threadsincreasing as the diameter of the roll increases, the thread to beproduced on the bolt remaining the same. Thus, in the rolls represented,and having three times the diameter of the bolt to be screwed, thethreads on the rolls have a rise three times as great as that to beproduced on the bolt, each of the rolls having three equidistantthreads. If the rolls were of a diameter four times as great as that ofthe bolt to be screwed then the screw-threads on the said rolls wouldhave a pitch four times as great as that of the thread to be produced onthe bolt, and there would be four of the said screw-threads on each ofthe rolls, and so on for other proportions. It is only by adopting therelative proportions described that the bolt under operation has notendency to advance into or out of the machine during the formation ofthe thread, a condition necessary to the correct figure and uniformpitch of the screw-thread formed.

Fig. 3 is a diagram illustrating the construction of the rolls, the saiddiagram represent ing the cylindrical surface of one of the rolls openedout, or uncoiled, or opened flat, and the inclined parallel linesrepresented indicate the inclination and distance apart of thescrewthreads formed on the roll.

Fig. 4 represents, in plan, one of the rolls and. the screwed boltbeingoperated upon, and

shows the parallelism of the single thread produced on the bolt B withthe threads on the roll 0.

Although I have found in practice that the mechanism described andrepresented for producing the rising and falling parallel motion of thetop roll answers every purpose yet I do not limit myself to the use ofthat particular arrangement, as other equivalent mech anicalarrangements may be adopted for producing a like motion in the top roll.

Having now described the nature of my invention, and the manner in whichthe same is to be performed, I wish it to be understood that I do notlimit myself to the precise details herein described and illustrated, asthe same may be varied without departing from the nature of myinvention; but

I claim as my invention of new or improved machinery for the manufactureof screws- 1. The combination of a series of rolls having screw threadsformed on them, which screw-threads have a proportion both in number andpitch to the screw-thread to be produced on the bolt operated uponsimilar to the proportion between the diameter of the said rolls and thebolt operated upon-that is, if the rolls have a diameter three times thediameter of the said bolt the said rolls have three equidistantscrew-threads, each thread having a pitch three times as great as thatof the thread to be produced, substantially as hereinbefore described,and illustrated in the accompanying drawings.

2. In combination with rolls having screwthreads upon them proportionatein number and pitch to the screw-thread to be produced on bolts to beoperated upon, as before described, the eccentric or equivalent meansfor the automatic rising and falling of one, in relation to the other,of said rolls, substantially as herein shown and set forth.

THOS. RIOKETT. n s.]

Witnesses:

GEORGE SHAW, RICHARD SKERBETT,

37 Temple Street, Birmingham.

